Abstract
The excretion of ethynyl steroids in milk from a lactating woman taking a daily dose of an oral contraceptive (Conlumin ®) containing 1 mg of norethindrone and 50 μg of mestranol has been studied. Milk was diluted with aq. triethylamine sulphate and steroids were extracted on a Sep-Pak C 18 cartridge at 60–64°C. Groups of unconjugated steroids, glucuronides, mono- and disulphates were separated on triethylaminohydroxypropyl Sephadex LH-20. Following hydrolysis and further purification, steroids possessing an ethynyl-substituent were isolated by chromatography on sulpho-hydroxypropyl Sephadex LH-20 in silver form. Gas chromatographic-mass spectrometric analysis of the O-methyloxime-trimethylsilyl ether derivatives of these steroids, showed the presence of norethindrone and mestranol in the free fraction and of tetrahydro metabolites of norethindrone with 3α,5α, 3α,5β and 3β,5α configurations in the mono- and disulphate fractions. The disulphate of the 3α,5α isomer was the most abundant ethynyl steroid in milk after 13 days of administration. The site of conjugation of the monosulphates was established by acetylation prior to solvolysis and analysis by gas chromatography-mass spectrometry. This showed that the 3α,5α isomer was conjugated mainly in the 17β-position while the 3α,5β isomer was conjugated at C-3.
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